Jib assembly

Abstract

A jib assembly is disclosed, for use with an articulated boom carried by an aerial device, having a compact configuration of components which allows a high degree of freedom in the rotation of the jib in the vertical plane and reduced obstruction of the rotational adjustment of the bucket carrier on the boom in the horizontal plane, relative to existing arrangements. A chain and sprocket arrangement driven by a hydraulic motor powers rotation of the jib coaxially with the bucket shaft and, where a winch is used, with the axis of rotation of the winch. The arrangement simplifies the routing of hydraulic hoses and affords a more compact and less cluttered arrangement of components at the tip of the boom, which has safety advantages in the environment of a tight distribution of power lines, where distances between live and grounded apparatus are small.

I claim: 
     
       1. An improved jib assembly for use with an articulated boom carried by an aerial device, said boom carrying a workperson carrier on a freely rotatable shaft extending through the boom, the jib assembly comprising: a jib, a jib sleeve mounted on said shaft for rotation about said shaft, said jib being carried slidably and lockably in said jib sleeve, a chain speed reducer, a motor for driving said chain speed reducer and a connector for connecting said chain speed reducer to said jib sleeve and for rotating said jib sleeve to provide a continuous range of rotation of said jib in a vertical plane as said sleeve is rotated by said motor through said chain speed reducer and connector;   said chain speed reducer further comprising at least one chain and one pair of sprocket wheels, one of said sprocket wheels being a rotation output sprocket wheel coaxial with said shaft, attached to a wall of said jib sleeve, freely rotatable in relation to said shaft, and connected to said connector.   
     
     
       2. An improved jib assembly according to claim 1, further comprising a winch which is coaxial and freely rotatable with respect to both said shaft and said rotation output sprocket wheel, the central cross-section of said winch being coplanar with said vertical rotation plane of said jib. 
     
     
       3. An improved jib assembly according to claim 2, wherein said motor for driving the rotation of said jib is a hydraulic motor mounted to said boom so that substantially the entire length of cable for circulating hydraulic fluid for said motor extends along the inside of said beam. 
     
     
       4. An improved jib assembly according to claim 2, wherein said connector comprises a plate rotatable coaxially with said rotation output sprocket wheel. 
     
     
       5. An improved jib assembly according to claim 2, wherein said chain speed reducer is a multiple chain speed reducer comprising, at each stage of speed reduction from said hydraulic motor to said rotation output sprocket wheel, a pair of sprocket wheels operatively connected by an associated endless loop of chain, said rotation output sprocket wheel belonging to a final pair of operatively connected sprocket wheels at the last stage of speed reduction. 
     
     
       6. An improved jib assembly according to claim 5, wherein all but the final pair of sprocket wheels and their associated chains in said multiple speed chain reducer are disposed inside said boom. 
     
     
       7. An improved jib assembly according to claim 5, wherein said winch is driven by a second hydraulic motor through a second speed reducer, both said second motor and said second speed reducer being disposed inside said boom. 
     
     
       8. An improved jib assembly according to claim 6, further comprising a sleeve member operatively connecting said winch to said second speed reducer at each end of said sleeve member, said sleeve member being mounted on said shaft and extending therealong through a side wall of said boom, through said rotation output sprocket wheel and through said connecting plate, so as to be freely rotatable in relation to said shaft, said boom and said rotation output sprocket wheel.   
     
     
       9. An improved jib assembly according to claim 7, wherein said second speed reducer comprises a worm gear and a worm for rotating said worm gear, said worm being connected to and driven by said second motor, said worm gear being rotatably mounted on said shaft and connected to said sleeve member.